Ornithischian¹ dinosaurs are one of the two major subdivisions of the Dinosauria, and consists of predominently herbivorous dinosaurs.

Iguanodon

Although the first Iguanodon was discovered near Cuckfield, there are several different species of Iguanodon. These include not only Iguanodon anglicum, but also Iguanodon ottingeri, Iguanodon mantelli, Iguanodon gracilis, Iguanodon lakotaensis, Iguanodon hoggi, Iguanodon dawsoni, Iguanodon fittoni, Iguanodon orientalis and Iguanodon seeleyi².

Two different species of Iguanodon have been found on the Island, Iguanodon atherfieldensis and Iguanodon bernissartensis, and they are the two species of Iguanodon that are well known. Iguanodon Atherfieldensis is named after Atherfield Point on the Island, the location where the type specimen was found. The major differences between the two species of Iguanodon are differences in the structure of the skull, pelvis and feet.

Iguanodon remains were first identified on the Island in 1829.

Iguanodon Atherfieldensis

Iguanodon atherfieldensis, translated as Atherfield's Iguana-tooth, was first discovered by Reginald Hooley in 1917, and has been discovered not only on the Island, but also on the mainland, Belgium, Spain, France and Germany. It grew
to between 6 and 7 metres long.

In comparison to other Iguanodons, Iguanodon atherfieldensis has a relatively low skull, forelimbs that are 50% the length of the hind limbs, and a short thumb spike. This type of Iguanodon was suited for low-level browsing and grazing.

Iguanodon bernissartensis

In 1878, in what is without doubt one of the greatest dinosaur finds ever, nearly 40 skeletons of Iguanodons were found in a coal mine in Bernissart, Belgium, 26 of which were complete. Using these dinosaurs, Louis Dollo constructed Iguanodon as a kangaroo-like biped, a view that continued into the 1960s, but realised that Iguanodon did not have a nose-horn, but a thumb spike.

Iguanodon bernissartensis, like atherfieldensis has been found on the Isle of Wight, Sussex, Belgium, France, Spain and Germany, many complete skeletons are on display in the Institut Royal des Sciences Naturelles de Belgique, and
examples from the Isle of Wight are on display in the Natural History Museum and Dinosaur Isle.

Larger than Iguanodon atherfieldensis, growing to between 10 and 13 metres long, its forelimbs are 75% the size of it's hind limbs. It also had large, robust hands and an elongate thumb-spike. It is believed that it was able to not only graze at ground level, but up to 6 metres off the ground, including the ability to crop from trees.

Hypsilophodon foxii

Hypsilophodon foxii, meaning Fox's high-crowned tooth³, was a small, fast biped.

The first specimen was discovered on the Island by William Buckland in 1832, yet both he and Sir Richard Owen considered them to be a juvenile Iguanodon. Reverend Fox noted several differences to Iguanodon, and considered it to be a new species, a view confirmed by Thomas Huxley, who named Hypsilophodon after him.

Hypsilophodons have only been found on the Isle of Wight, where palaeontologist Dr Dave Martill of Portsmouth University feels that as many as 5,000 Hypsilophodon specimens exist, all of which drowned when trapped in a tremendous flash flood.

Most Hypsilophodon skeletons on the Island average around 1.5 metres long, although it is believed that they grew as large as 2.3 metres long, as most of the skeletons so far discovered appear to be of juveniles, with the exception of a single, much larger, example. Although initially believed to have been able to climb trees and cliffs, it is more likely that Hypsilophodon was a
ground-dwelling browsing omnivore, eating insects, small animals and vegetation, and capable of moving at speed.

Valdosaurus canaliculatus

Valdo means Weald and canaliculatus refers to the canal between the two condyles at the end of the femur. Valdosaurus has only been discovered on the Isle of Wight, Sussex and Romania, and specimens are in the Natural History Museum and the Isle of Wight Museum of Geology.

Valdosaurus was around 1.5 metres tall at hip level, and 3.5-5 metres long. It was a herbivore which ate leaves, feeding from ground level to about 2 metres off the ground. Like Iguanodon, it could walk either quadrupedally or bipedally.

Yaverlandia bitholus

Yaverlandia bitholus is, so far, the only Pachycephalosaur to have found on the Isle of Wight, in Yaverland, as the name suggests. Pachycephalosaurs were "thick headed" dinosaurs who are believed to have used their thick, domed skull as a weapon. Yaverlandia is believed to have been one of the earliest, and most primitive and unusual, pachycephalosaur. Only one other Pachycephalosaur has been found in Europe, a tooth found in Portugal that has been named Taveirosaurus costai.

The species name of Yaverlandia bitholus, meaning twin-domed, is a reference to the skull's unique twin frontal bones. The only specimen discovered so far was a skull discovered in Yaverland, Isle of Wight. This suggests, when compared to other pachycephalosaurs, is likely to be no more than 2 metres long, but H.D. Sues feels this may belong to a juvenile, and a fully grown Yaverlandia may have been larger.

Stegosaur

A pubis discovered on the Isle of Wight has been identified as belonging to a stegosaur, but which species of stegosaur it belongs to, or indeed, whether it is a new species of stegosaur, is unknown. Many scientists believe it could belong to Regnosaurus Northamptoni, the first stegosaur remains to be discovered in 1838. This discovery initially caused much confusion as only a right mandible was recovered. It was at first believed to belong to Hylaeosaurus, although it was also believed to be from either an Iguanodon or a sauropod, but has recently been confirmed as belonging to a stegosaur.

Other stegosaurs so far discovered include Kentrosaurus, Huayangosaurus, Craterosaurus and, of course, Stegosaurus, first discovered in 1877.

Regnosaurus is perhaps the most likely Stegosaur for this bone as it was first discovered in the Wealden of Sussex, but the Isle of Wight pubis can only be classified as "Stegosaur indeterminate" until more complete skeletons are discovered.

However, scientists believe that the stegosaur was approximately 4 metres long, and would not only eat at ground level, but be able to rear up and eat higher vegetation.

Polacanthus foxii

Polacanthus foxii, meaning Fox's Many-Spined, was discovered by Reverend Fox on the Isle of Wight in 1865. So far, three Polacanthus foxii specimens have been
found, two on the Isle of Wight, and one in Dorset.

Other species of Polacanthus may have existed, possibilities include Polacanthus rudgwickensis, found in Rudgwick, in Surrey, with other possible members of the Polacanthidae including the American Hoplitosaurus and a newly-discovered specimen found in
Spain. Specimens exist in the Natural History Museum, Sedgwick Museum in Cambridge and Blackgang Chine.

Polacanthus foxii was over 5 metres long, with a low, arched profile, covered in spines and an armoured shield ensured it was well-protected. It was a herbivore, and probably ate close to the ground. A Polacanthus foxii can be seen in "Walking With Dinosaurs: Giants Of The Skies", and on the BBC's "Walking With Dinosaur's" website.

Hylaeosaurus armatus

Hylaeosaurus, or "forest-lizard", was the third dinosaur to be discovered, in 1833. Along with Iguanodon and Megalosaurus, was one of the original three dinosaurs in the Dinosauria. Hylaeosaurus, like Polacanthus, is an armoured anklosaur, with large spikes and pointed armour plates. It was a for a long time considered to be the same genus as Polacanthus, but recent study has shown that Hylaeosaurus does not have a co-ossified scapukocoroid, and there are also differences in the shape of the tibia and the arrangement of armour. Also unlike Polacanthus, it did not have a sacral shield of fused osteoderms.

Initial belief that Hylaeosaurus and Polacanthus were the same genus and species occured largely because the first Polacanthus specimen consisted only of the hindparts, and the first Hylaeosaurus discovered consisted only of the foreparts.

Due to this confusion, Hylaeosaurus has been thought of as being discovered on the Isle of Wight, when in fact the Isle of Wight remains were those of Polacanthus. It is, however, possible that a Hylaeosaurus will be discovered on the Island.

Hylaeosaurus was smaller than Polacanthus, approximately 4 metres long, with probably a similar diet to Polacanthus.

Dinosaurs Of The Isle Of Wight

• Dinosaurs of the Isle of Wight
• Dinosaurs of the Isle of Wight: Why The Island Is Special
• Dinosaurs of the Isle of Wight: Dinosaur Hunters
• Dinosaurs of the Isle of Wight: Ornithischians
• Dinosaurs of the Isle of Wight: Sauropods
• Dinosaurs of the Isle of Wight: Theropods
• Dinosaurs of the Isle of Wight: Pterosaurs
• Dinosaurs of the Isle of Wight: Live From Dinosaur Island